Apparatus for drilling and sampling rock formations

ABSTRACT

A double walled drill stem has a fluid driven piston on one end thereof which, by porting, reciprocates and strikes an anvil carrying a bit. The fluid exhausts downwardly around the bit and drives chips and the like upwardly through the inner portion of the drill stem, the fluid to drive the piston passing downwardly between the inner and outer drill stem members, the exhausted fluid carrying chips and dust and the like upwardly to the surface in a continuous manner.

United States Patent 1191 Oughton I 1 Mar. 5, 1974 I541 APPARATUS F L N AND 3,208,539 9/1965 Henderson 175 215 SAMPLING ROCK FQRMATIONS 3,280,925 10/1966 Becker ct al... 175/215 X I 3,299,971 H1967 Lewis 1 1 175/92 1 Inventor: Ronald ()ughton, g ry, A 3,473,617 10/1969 Elenhurg 175 215 Canada [73] Assignec: Shuttle Mountain Holdings Co. Ltd.,

Letheridge, Alberta, Canada [22] Filed: June 15, 1972 [21] Appl. No.: 263,176

[52] U.S.VCI. 175/215, 175/92 [51] Int. Cl E2111 21/00, E2lb 17/00 [58] Field of Search 175/215, 60, 207, 212, 92,

[56] References Cited UNlTED STATES PATENTS 3,208,538 9/1965 Pitcher 175/215X Primary Examiner[)avid H. Brown Atlrirne Agent, or Firm-Stanley (i. Ade

[57] ABSTRACT A double walled drill stem has a fluid driven piston on one end thereof which, by porting, reciprocates and strikes an anvil carrying a bit. The fluid exhausts downwardly around the bit and drives chips and the like upwardly through the inner portion of the drill stem, the fluid to drive the piston passing downwardly between the inner and outer drill stem members, the

exhausted fluid carrying chips and dust and the like upwardly t0 the surface in a continuous'manner.

13 Claims, 11 Drawing Figures PATENTEDMAR 51914 3,795,283

SHEET 2 BF 3 FIG.7

PATENTED 5 I974 SHE-ET a nr 3 f m m FIG. ll

FIG. IO

FIG. 9

BACKGROUND OF THE INVENTION Conventionally, percussive drills utilize a fluid such as air or drilling mud passing downwardly of the drill stem to the bit. This picks up debris formed by the bit and drives it upwardly around the outside of the drill stem between the wall of the hole being formed and the drill stem. This often results in dislodging further particles in the wall of the bore and under certain circumstances can cause collapsing of the bore. Conventional devices often use valves or the like to provide the percussive impact needed at the drill bit and these are easily clogged or jammed by particles of rock formed during the drilling operation. This of course means that the entire drill string has to be removed so that the clogging can be cleared.

Also when coring, it is conventional to use a reduced diameter core guide but ifthe core is not uniform, it will lodge in the reduced section of the inner core passage. This is often-prevalent when a small layer of clay,

etc. is reached during the drilling operation.

Conventional porting to the outside of the drill bit not only results, under certain circumstances, of caveins but also these ports can let in water which can enter the internal mechanism thus makingit impossible to continue or to finish a hole whenthedrilling fluid is shut off'in order to "add'on "additional lengths of drill stem.

SUMMARY OF THE INVENTION The principle object and essence of the invention is to provide a device of the character herewithin described which enables a piston to bereciprocated by fluid under pressure andthen the fluid to be exhausted downwardly and internally to the bit whereupon it picks up the chips and the like formed by the bit and exhausts'them upwardly through the centerof the assembly to the surface in a continuous manner.

Another object of the invention is to provide a device of-the characterherewithindescribed which eliminates all contact of the drilling fluid with the wall of the bore formed thus preventing'cave-ins from occurring.

Yet another object ofthe invention is to provide a device of the character herewithin described which eliminatesall-valves inasmuch asautomatic porting is provided for-the routing of the pressurefluids A yet further object of the invention is to provide a device of the character herewithin'described which is easily used for standard coring practices if desired.

Yet another object of the invention is to provide a device of the character herewithin described inwhich additional sections of the drill stemcan easily be added to those already in the bore." I I .A still further object of the invention is to provide a device ofthe character herewithindescribed which, be-

cause of the lack of moving parts, does not become inoperation and otherwise well suited to' the purpose for which it is designed.

With the considerations and inventive objects herein set forth in view, and such other or further purposes, advantages or novel features as may become apparent from consideration of this disclosure and specification, the present invention consists of the inventive concept which is comprised, embodied, embraced, or included in the method, process, construction, composition, arrangement or combination of parts, or new use of any of the foregoing, herein exemplified in one or more specific embodiments of such cOncepLrefere'nce bein had to the accompanying Figures in which:

DRAWINGS FIG. 1 is a longitudinal sectional view of the invention. I

FIG. 2 is a sectional view of the invention shown within a bore hole and reduced in scale with reference to FIG, 1.

FIG. 3 is a cross sectional view of the anvil per se substantially along the line 33 of FIG. 1.

FIG. 4 is a cross' sectional view of the outer shell or sleeve per se substantially along the line 4-4 of FIG. 1.

FIG. 5 is a cross sectional view along the line 5-5 of FIG. 1.

FIG. 6 is a side elevation of the anvil per se;

FIG. 7 is a fragmentary cross sectional view of one end of the outer shell or sleeve shown secured to one end of the outer casing.

FIG. 8 is a cross sectional view of the bit substantially along'the line 88 of FIG."1. I

FIGS. 9, l0 and 11 show fragmentary side elevations of the three methods for providing rotation to the drill stern. v

In the drawings like characters of reference indicate corresponding parts in the different figures.

PRELIMINARY DESCRIPTION The device consists of outer and inner concentrically spaced drill stern section 10 having an outer casing l l screw threadably secured to the outer section of the drill stem section 10 with a piston and cylinder assemblyl2 mounted within the casing so that the piston can reciprocate and strike an anvil I3 which in turn has a drill bit assembly 14 secured to the outer end thereof and beyond the end of the casing 11. The piston reciprocates and strikes the anvil whichin turn reciprocates with thebit in a percussive manner.

DETAILED DESCRIPTION In detail, reference should first be'made to FIG. 2 which shows the assembly within a bore 15 formed within rock bearing-formations l6 and extending downwardly from ground level 17. v r I I it I The drill string sections 10 terminate at an air swivel assembly 18 which is conventional in construction and includes an air intake 19 which is connected toa source of fluid under pressure. This fluid may, of course, be drilling mud or air but under' n or nial circumstances is usually air.

An extension 20 extends upwardly from the inner I portion of the drill stem sections and terminates in a discharge 2] through which chips and fluid are discharged in a continuous basis as will hereinafter be described.

A conventional collar assembly "or ground seal 22 mounts the device at ground level in the usual way, to seal anyfluid (air) which may otherwise escape to the cally within the outer section and being maintained in.

the desired concentric relationship by means of a spider 25 situated at either end thereof. These sections can therefore be. added one to the other as a complete unit rather than individual inner and outer sections.

Under normal circumstances, the air intake 19 enters through the air swivel assembly 18 to the annular space 26 formed between the inner and outer sections 24 and 23, it being understood that the spiders 25 are apertured to permit passage of the fluid under pressure thereby.

'Means collectively designated 27 are provided to connect the outer casing 11 with the lowermost drill stem section 10 and takes the form of a cylindrical adaptor sleeve 28 being screw threaded externally to the one end of the outer section 23 as clearly shown in FIG: 1 so that the outer wall of the sleeve 28 and the section 23 are flush."

The lower end 29 of the adaptor sleeve is reduced in diameter and screw threaded to receive the end 30 of the outer casing 11 which screw threadably engages same so that the outer wall of casing 11 is flush with the outer wall of the sleeve 28.

Forming part of the adaptor sleeve 28 is a compression head 31 which is cylindrical and an inner cylindrical casing 32 is shouldered as at 33 to engage within a shouldered portion 34 of the compression head. It then engages the end 35 of the inner section 24 of the lowermost drill stern section 10 as clearly shown.- In this 'connection split rings36 secure the inner casing 32 to the end 35 of the drill stem section 24 and also to the end 37 of the compression head 31.

The cylinder 38 of the piston and cylinder assembly 12 is in'turn secured by the means ofa rubber ring 39 to the other end of the compression head and extends downwardly therefrom as clearly shown.

Longitudinally extending ports or channels 40 are formed within the compression head and extend from the end 37- thereof to radially extending ports 42 formed adjacent the other end of the compression head and extending outwardly to the outer wall thereof. These ports and channels 40 and 42 communicate between theannular space 26 of the drill stem sections and a longitudinally extending annular channel 43 formed between the cylinder 38 and the inner wall of the outer cylindrical casing 30, said annular channel extending from adjacent ports 42 to a location indicated by reference character 44-.

The piston 45 of the piston and cylinder assembly 12 is cylindrical in configuration and engages around the inner cylindrical casing 32 and within the cylinder 38.

Conventional anti-frictional means (not illustrated) are provided to reduce the sliding friction between the piston and the casing on the one hand and the piston and the cylinder on the other.

This piston is provided with a plurality of longitudinally extending channels or ports 46 extending from the head 47 thereof, along the length thereof to exterior radially situated ports 47' which extends through the outer wall of the piston as-clearly shown.

Also provided on the piston 45 is an annular open ended channel 48 formed by a reduction of the diame- 4 ter of the cylinder below thehead 47, this reduced diameter and the cylinder wall 38 defining this channel 48 A plurality of ports 49 are formed through the cylinder wall 38 adjacent the lower end 50 thereof.

The outer casing 11 is provided with an annular shoulder 51 adjacent the end 50 of the cylinder which is retained therein by means of a rubber ring 52 in the usual manner and this annular shoulder acts as a fluid pressure seal at this point.

However, the casing increases in diameter below this shoulder to form an annular fluid passageway 52' which extends to adjacent the internally screw threaded end 53 of the outer casing l1.

Describing the operation of the piston and cylinder assembly. fluid under pressure is supplied downwardly through the outer annular space 26 between the outer and inner sections of the drill stem assembly 10. It is then routed through the passageways 40 and ports 42 in the compression head 31, to the annularchannel 43 between the cylinder 38 and the outer casing 11.

It then passes through the radially extending ports 49 formed in the cylinder wall adjacent the end 50 and enters the annular chamber 48 between the wall and the piston, reacting between the shoulder 51 of the outer casingand the undersideof the head 47 of the piston thus driving it in the direction of arrow 54 towards the compression head 31. i

The piston moves in this direction, exhausting air through ports 46 and 47' until ports 47' are covered by the annular shoulder 51 at which time air in front of the piston head is compressed between the head and the compression head 31. This compressed air acts a buffer and prevents the head of the piston striking the compression head 31. However, the piston moves towards the compression head 31 a distance sufficient to permit ports 47' to align with ports 49 in the cylinder wall at which time the fluid will be routedfrom the annular space 43, through ports 49, through ports 47' and channels 46 to the upper side of the piston head within the compression chamber defined by the piston head and the compression head 31. This immediately reverses the action of the piston reinforced by the compression of the air between the piston and the compression head and drives the piston downwardly or in a direction opposite to arrow 54 until'it reaches the position shown in FIG. 1 whereupon the sequence'repeats.

It hasbeen found that with approximately psi fluid pressure, a reciprocating rate for the piston can be obtained of approximately 3,200 strokes per minute.

Each time the position reaches the position shown in H6. 1, the end 55 thereof strikes the anvil assembly 13.

A cylindrical anvil sleeve or outer shell 56 is screw threadably engaged within the end 53 of the outer casing 11 and the anvil 13, which is cylindrical in configuration, is mounted between this shell and the inner casing 32 for percussive reciprocation thereon.

The anvil is shown in detail in FIGS. 3 and 6. It consists of a cylinder 57 having a plurality of radially extending bearing lugs 58 formed onone end thereof and ascrew threaded portion 59 formed on the other end. A plurality of closed ended longitudinally extending slots 60 are formed within the wall of the cylindrical portion 57 intermediate the ends thereof.

The outer shell or anvil sleeve 56 is also cylindrical and a plurality of longitudinally extending portions 61 are formed on the inner surface'thereof also having longitudinally extending slots 62 closed at one end thereof,

. the annular fluid passageway 52 and a further passageway 63' formed adjacent the end 64 of the anvil shell 56. i

A bit assembly 65 screw threadably engages the screw threaded end 59 of the anvil and is a sliding fit within the end 64 of the anvil sleeve as clearly shown in FIG. 1.

An annular flexible seal 66 extends between the anvil I shell 56 and the anvil adjacent the annular space 63' and this seal is engaged with the wall of the anvil in such a manner that fluid under pressure can pass thereby downwardly towards the bit assembly 65 but fluid or debris cannot pass upwardly.

The :bit assembly is conventional in construction insofar the material and attachment of the bit inserts 67'are concernedQHowever, it is provided with a plurality oflon gitudinally extending channels 68 extending from the inner end of the bit to cross channels 69 which extend inwardly to the inner bore 70 of the bit. The channels 68'also communicate with a plurality of further channels 71 which extend to the face of the bit.

It will of course beunderstoo'd that the hollow center 70 of'the bit communicates with the interior of the inner casing 32 and thence to the inner section 24 of the drill stem component 10.

' In operation, air reciprocates'the piston as aforesaid and is exhausted downwardly" through the annular channel 52, past the anvil 13 to the annularchannel 63 whereupon it' passes through the bit assembly 65 whereupon part of the air or fluid enters the inner bore 70 of the bit and moves upwardly therefrom forming a jet action. Other air or fluid passes through the longitudinal drilling 71 to the face of the drill bit and picks up chips or debris and drives them towards the inner bore whereupon they are picked up by'the jet action of the air passing upwardly through the assembly to the surface to be discharged through the discharge 2] in a continuous manner.

Under these circumstances, there is no chance of the fluid disturbing the walls of the bore being formed thus eliminating the majority ofcauses of cave-ins and the like. Furthermore, due to the fact that the only moving part is the reciprocal piston and the percussively reciprocating anvil, there is no chance of dust ordebris interfering with the action of the device inasmuch no moving valves are required.

If it is desired to core, a coring bit of special design is placed on the end of the anvil'and coring can be undertaken in the conventional manner.

Under certain circumstances,-a single wall drill stem section may be used. If this is so, then the anvil would be solid at the lower end thereof so that the fluid would pass outwardly of the drill bit and thenupwardly between the drill bit and the drill stem in the conventional manner. I v

However. the preferred embodiment provides for the passageway of the fluid and thechips centrally through the drill stemto be discharged externally as hereinbel'ore described.

It should of course be mentioned that the apparatus can be used in any position as the operation does not rely on gravity for any portion of the action.

The conventional anti-friction means mentioned above, also includes anti-frictional material used in the construction of the casing and cylinder thus eliminating the requirements for oil of any kind in the apparatus. This in turn eliminates contamination which is a problem normally caused by conventional type apparatus operating in a similar environment.

FIGS. 9, 10 and 11 illustrate three methods of providing the necessary rotation to the drill stern.

In FIG. 9, 72 illustrates the conventional supporting derrick or framework. A top drive assembly collectively designated 73 powered by hydraulic air or electricity, causes rotation of the double walled pipe 74 which in turn connects through the ground seal 22, to the drill stem (not shown in FIGS. 9, l0 and 11). In

FIG. 10, a conventional rotary swivel assembly collec- I tively designated 75 is provided with a modified top discharge swivel connected to discharge 21 and this again rotates the double walled pipe 74, through the ground seal 22.

In FIG. 11, the conventional rotary table 76, rotates a conventional kellybar 77 terminating in a conventional rotary swivel assembly 75 at'thc upper end thereof. A gear or chain drive assembly collectively designated 78 includes a gear 79 rotated by the kelly bar 77 and this in turn engages a further gear 80which is. connected to a double walled pipe or kellybar 81 through the air inlet swivel assembly 18 and thence through the ground seal 22, to the drill stem. The discharge assembly 21 is connected through a special dis charge swivel, to the upper end of this double wall kelly I to which the inventor hereof is entitled asjustice dictatcs.

What I claim as my invention is: l

I. A drilling assembly including outer and inner concentrically spaced drill stem sections and a source of fluid under pressure supply to said drill stem section between the outer and inner walls thereof; comprising in combination an outer casing, means of securing said casing by one end thereof to one end of the outer section of said drill stem section, a piston and cylinder assembly mounted within said casing, an anvil reciprocal within said casing, thepiston of said piston and cylinder assembly adapted to strike one end of said anvil, and a drill bit assembly operatively secured to the other end of said anvil beyond the other end of said casing, means cooperating between said casing and said piston and cylinder assembly to route fluid under pressure to each side of said piston alternately to reciprocate same whereby said piston strikes said anvil successively, and means mounting said anvil within said casing for percussive reciprocation therein, said means mounting said anvil for percussive reciprocation within said casing including a plurality. of balls engaging between said anvil and said casing, longitudinal channels formed in the wall of said anvil and in said casing, said balls being mounted in said channels, and fluid passageway means between said anvil and said casing communicating between each side of said anvil.

2. The assembly according to claim 1 which includes an anvil sleeve screw threadably engageable with the lower end of said casing and forming part thereof, said anvil reciprocating within said sleeve.

3. The assembly according to claim 1 in which said means securing said casing by oneend thereof to one end of the outer section of said'drill stem section including an adaptor sleeve screw threadably engaging said outer section and screw threadably engaging said casing, a ported compression head forming part of said adaptor sleeve and being secured by one end thereof to 7 one end of the inner section of said drill stern section,

the cylinder of said piston and cylinder assembly being secured by one end thereof to the other end of said compression head and by other end thereof internally said'casing and said cylinder communicating with said ported compression head. I

4. The assembly accordingto claim 3 which includes an inner cylindrical casing secured within said compression head and to said one end of the inner section of said drill stem section, said piston being cylindrical and reciprocating upon said inner casing and within said cylinder, said cylinder and said compression head defining an annular compression chamber.

5. The assembly according to claim 4 in which said piston includes fluid connecting means extending from the head thereof along the length thereof to exterior ports in the wall of said piston, further ports formed in the wall of said cylinder adjacent one end thereof, said ports in said cylinder and in said piston aligning when said piston is at one end of the stroke thereof.

6. The assembly according to claim 1 which includes means routing internally the exhausted fluid from said piston and cylinder assembly to said bit assembly, and means communicating between said bit assembly and the inner section of said drill stem section whereby said exhausted fluid picks up chips and the like'formed by said bit assembly and exhausts same through said inner drill stem section. I

7,. The assembly according to claim 6 in which said means securing said casing by one end thereof to one end of the outer section of saidv drill stem section includes an adaptor sleeve screw threadably engaging.

said outer section and screw threadably engaging said casing, a ported compression head forming part of said adaptor sleeve and being secured by one end thereof to I one end of the inner section of said drill stem section, the cylinder of. said piston and cylinder assembly being secured by one end thereof to the other'end of said compression head, said cylinder being secured by the other end -thereof internally to said casing, ports formed between the inner wall of said casing and said cylinder communicating with said ported compression head.

8. The assembly according to claim 1 which includes an inner cylindrical casing secured within said compression head and to said one end of the inner section of said drill stem section, said piston being cylindrical and reciprocating upon saidiinner casing and within to said casing, ports formed between the inner wall of said cylinder, said cylinder and said compression head defining an annular compression chamber.

9. The assembly according to claim 8 in which said piston includes fluid connecting means extending from the head thereof along the length thereof to exterior ports in the wall of said piston, further ports formed in the wall of said cylinder adjacent one end thereof, said ports in said cylinder and in said piston aligning when said piston is at one end of the stroke thereof.

10. A drilling assembly including outer and inner concentrically spaced drill stem sections and a source of fluid under pressure supply to said drill stem section between the outer and inner walls thereof; comprising in combination an outer casing, means securing said casing by one end thereof to one end of the outer section of said drill stem section, a piston and cylinder assembly mounted within said casing, an anvil reciprocal within said casing, the piston of said piston and cylinder assembly adapted to strike one end. of'said anvil, and a drill bit assembly operatively secured to the other end of said anvil beyond the other end of said casing, means cooperating between said casing and said piston and. cylinder assembly to route fluid under pressure to each side of said piston alternately to reciprocate same whereby said piston strikes said anvil successively, and means mounting said anvil within said casing for percussive reciprocation therein, said means securing said casing by one end thereof to one end of the outer section of said drill stem section including an adaptor sleeve screw threadably engaging said outer section and screw threadably engaging said casing, a ported compression head forming part of said adaptor sleeve and being secured by one end thereof to one end of the inner section of said drill stem section; the cylinder of said piston and cylinder assembly being secured by one end thereof to the other end of said compression head,

and by the other end thereof internally to said casing, ports formed between the inner wall of said casing and said cylinder communicating with said ported compression head, an inner cylindrical casing secured within said compression head and to said one end of the inner section of said drill stem section, said piston being cylindrical and reciprocating upon said inner casing and within said cylinder, said cylinder and said compression head defining an annular compression chamber, said means mounting'said anvil for percussive reciprocation within said casing including an anvil sleeve secured to said casing at one end thereofand forming part thereof, said anvil being of cylindrical configuration and reciprocating upon said inner casing and within said sleeve, at least one closed ended longitudinally extending channel formed in the inner wall of said sleeve, corresponding channels formed in the outer wall of said anvil and ball bearings mounted in said channels forjournalling said anvil within said sleeve as aforesaid, and fluid passage means between said anvil and said sleeve communicating upon each sideof said anvil.

11. The assembly according to claim 10 which includes. means routing internally the exhausted fluid from said piston and cylinder assembly to said bit assembly, and means communicating between said bit as- .sembly and the inner section of said drill stem section within said casing including a plurality of balls engaging between said anvil and said casing, longitudinal channels formed in the wall of said anvil and in said Casing, said balls being mounted in said said channels, and fluid passageway means between said anvil and saidcasing communicating between each side of said anvil. 

1. A drilling assembly Including outer and inner concentrically spaced drill stem sections and a source of fluid under pressure supply to said drill stem section between the outer and inner walls thereof; comprising in combination an outer casing, means of securing said casing by one end thereof to one end of the outer section of said drill stem section, a piston and cylinder assembly mounted within said casing, an anvil reciprocal within said casing, the piston of said piston and cylinder assembly adapted to strike one end of said anvil, and a drill bit assembly operatively secured to the other end of said anvil beyond the other end of said casing, means cooperating between said casing and said piston and cylinder assembly to route fluid under pressure to each side of said piston alternately to reciprocate same whereby said piston strikes said anvil successively, and means mounting said anvil within said casing for percussive reciprocation therein, said means mounting said anvil for percussive reciprocation within said casing including a plurality of balls engaging between said anvil and said casing, longitudinal channels formed in the wall of said anvil and in said casing, said balls being mounted in said channels, and fluid passageway means between said anvil and said casing communicating between each side of said anvil.
 2. The assembly according to claim 1 which includes an anvil sleeve screw threadably engageable with the lower end of said casing and forming part thereof, said anvil reciprocating within said sleeve.
 3. The assembly according to claim 1 in which said means securing said casing by one end thereof to one end of the outer section of said drill stem section including an adaptor sleeve screw threadably engaging said outer section and screw threadably engaging said casing, a ported compression head forming part of said adaptor sleeve and being secured by one end thereof to one end of the inner section of said drill stem section, the cylinder of said piston and cylinder assembly being secured by one end thereof to the other end of said compression head, and by other end thereof internally to said casing, ports formed between the inner wall of said casing and said cylinder communicating with said ported compression head.
 4. The assembly according to claim 3 which includes an inner cylindrical casing secured within said compression head and to said one end of the inner section of said drill stem section, said piston being cylindrical and reciprocating upon said inner casing and within said cylinder, said cylinder and said compression head defining an annular compression chamber.
 5. The assembly according to claim 4 in which said piston includes fluid connecting means extending from the head thereof along the length thereof to exterior ports in the wall of said piston, further ports formed in the wall of said cylinder adjacent one end thereof, said ports in said cylinder and in said piston aligning when said piston is at one end of the stroke thereof.
 6. The assembly according to claim 1 which includes means routing internally the exhausted fluid from said piston and cylinder assembly to said bit assembly, and means communicating between said bit assembly and the inner section of said drill stem section whereby said exhausted fluid picks up chips and the like formed by said bit assembly and exhausts same through said inner drill stem section.
 7. The assembly according to claim 6 in which said means securing said casing by one end thereof to one end of the outer section of said drill stem section includes an adaptor sleeve screw threadably engaging said outer section and screw threadably engaging said casing, a ported compression head forming part of said adaptor sleeve and being secured by one end thereof to one end of the inner section of said drill stem section, the cylinder of said piston and cylinder assembly being secured by one end thereof to the other end of said compression head, said cylinder being secured by the other end thereof internally to said casing, poRts formed between the inner wall of said casing and said cylinder communicating with said ported compression head.
 8. The assembly according to claim 1 which includes an inner cylindrical casing secured within said compression head and to said one end of the inner section of said drill stem section, said piston being cylindrical and reciprocating upon said inner casing and within said cylinder, said cylinder and said compression head defining an annular compression chamber.
 9. The assembly according to claim 8 in which said piston includes fluid connecting means extending from the head thereof along the length thereof to exterior ports in the wall of said piston, further ports formed in the wall of said cylinder adjacent one end thereof, said ports in said cylinder and in said piston aligning when said piston is at one end of the stroke thereof.
 10. A drilling assembly including outer and inner concentrically spaced drill stem sections and a source of fluid under pressure supply to said drill stem section between the outer and inner walls thereof; comprising in combination an outer casing, means securing said casing by one end thereof to one end of the outer section of said drill stem section, a piston and cylinder assembly mounted within said casing, an anvil reciprocal within said casing, the piston of said piston and cylinder assembly adapted to strike one end of said anvil, and a drill bit assembly operatively secured to the other end of said anvil beyond the other end of said casing, means cooperating between said casing and said piston and cylinder assembly to route fluid under pressure to each side of said piston alternately to reciprocate same whereby said piston strikes said anvil successively, and means mounting said anvil within said casing for percussive reciprocation therein, said means securing said casing by one end thereof to one end of the outer section of said drill stem section including an adaptor sleeve screw threadably engaging said outer section and screw threadably engaging said casing, a ported compression head forming part of said adaptor sleeve and being secured by one end thereof to one end of the inner section of said drill stem section, the cylinder of said piston and cylinder assembly being secured by one end thereof to the other end of said compression head, and by the other end thereof internally to said casing, ports formed between the inner wall of said casing and said cylinder communicating with said ported compression head, an inner cylindrical casing secured within said compression head and to said one end of the inner section of said drill stem section, said piston being cylindrical and reciprocating upon said inner casing and within said cylinder, said cylinder and said compression head defining an annular compression chamber, said means mounting said anvil for percussive reciprocation within said casing including an anvil sleeve secured to said casing at one end thereof and forming part thereof, said anvil being of cylindrical configuration and reciprocating upon said inner casing and within said sleeve, at least one closed ended longitudinally extending channel formed in the inner wall of said sleeve, corresponding channels formed in the outer wall of said anvil and ball bearings mounted in said channels for journalling said anvil within said sleeve as aforesaid, and fluid passage means between said anvil and said sleeve communicating upon each side of said anvil.
 11. The assembly according to claim 10 which includes means routing internally the exhausted fluid from said piston and cylinder assembly to said bit assembly, and means communicating between said bit assembly and the inner section of said drill stem section whereby said exhausted fluid picks up chips and the like formed by said bit assembly and exhausts same through said inner drill stem section.
 12. The assembly according to claim 10 in which said piston includes fluid connecting means extending from the head thereof along the length thereof to exterior ports in The wall of said piston, further ports formed in the wall of said cylinder adjacent one end thereof, said ports in said cylinder and in said piston aligning when said piston is at one end of the stroke thereof.
 13. The assembly according to claim 10 in which said means mounting said anvil for percussive reciprocation within said casing including a plurality of balls engaging between said anvil and said casing, longitudinal channels formed in the wall of said anvil and in said casing, said balls being mounted in said said channels, and fluid passageway means between said anvil and said casing communicating between each side of said anvil. 